Filter devices for receiving filter elements are readily available on the market in a plurality of embodiments, for example as disclosed in EP 1 287 871 A1 and EP 0 891 214 B1. A not insignificant portion of the production costs in these filter devices originates from the formation of the connecting unit which, in the operating state in which the filtration process can take place, establishes a suitable connection between the filter element and the respective fluid duct in the cover part. The connecting unit must be designed such that the installation processes for changing the filter elements are simple and uncomplicated, but that reliable sealing occurs, even at high pressure levels. Moreover, the connecting unit, as much as possible, should be made such that in the operation of the filter device “replacement reliability” is provided. In other words, a construction is desirable in which in view of the plurality of designs of filter elements on the market, only those filter elements specially adapted to the housing and the cover part can achieve an operating state. The risk that filter elements of an unintended type with unsuitable filter properties will then be inadvertently operated is avoided.